Multi-burst A-TRS for loop operation on SSB-free secondary cells in inter-band carrier aggregation

Abstract

Aspects of the present disclosure allow a UE to request a base station to configure and transmit A-TRS in an SSB-free secondary carrier on a different frequency band in an anchor carrier on one frequency band. The UE sends a request for an A-TRS in a first cell served by the anchor carrier. Based on the request, the UE receives the A-TRS in a second cell lacking SSB transmission served by the secondary carrier based on the request. The base station may also control transmission of the A-TRS in the SSB-free secondary cell based on a timer derived from the request. Using the A-TRS, the UE may apply AGC and time / frequency tracking loop operations prior to receiving a PDSCH in the SSB-free secondary cell, thereby improving reception performance of downlink data transmissions in the secondary carrier. Thus, network energy savings provided by SSB-free secondary carriers can be obtained in inter-band CA.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. non-provisional patent application No. 17 / 937,269, filed on September 30, 2022, entitled “MULTI-BURST A-TRS FOR LOOPOPERATION ON SSB-LESS SECONDARY CELL IN INTER-BAND CARRIER AGGREGATION,” which is expressly incorporated herein by reference in its entirety. Background Art Technical Field

[0003] The present disclosure relates generally to communication systems, and more particularly to wireless communication systems between user equipment (UE) and base stations.

[0004] introduction

[0005] Wireless communication systems are widely deployed to provide a variety of telecommunication services, such as telephony, video, data, messaging, and broadcast. Typical wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0006] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at a city, country, region, and even global level. An example telecommunication standard is 5G New Radio (NR). 5G NR is part of the continuous mobile broadband evolution promulgated by the Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with the Internet of Things (IoT)) and other requirements. 5GNR includes services associated with enhanced mobile broadband (eMBB), massive machine type communication (mMTC), and ultra-reliable low latency communication (URLLC). Certain aspects of 5G NR may be based on 4G Long Term Evolution (LTE) standards. It is necessary to further improve 5G NR technology. In addition, these improvements may also be applicable to other multiple access technologies and telecommunication standards that employ these technologies. Summary of the invention

[0007] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of these aspects. This summary is not an extensive overview of all contemplated aspects, and is neither intended to identify key or important elements of all aspects, nor to describe the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to a more detailed description presented later.

[0008] In one aspect of the present disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The apparatus includes: a processor; a memory coupled to the processor; and instructions stored in the memory and operable when executed by the processor to cause the apparatus to: send a request for an aperiodic tracking reference signal (A-TRS) in a first cell; and receive the A-TRS in a second cell lacking a synchronization signal block (SSB) transmission based on the request.

[0009] In one aspect of the present disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a base station. The apparatus includes: a processor; a memory coupled to the processor; and instructions stored in the memory and operable when executed by the processor to cause the apparatus to: receive a request for an A-TRS in a first cell; and transmit the A-TRS in a second cell lacking SSB transmission based on the request.

[0010] To achieve the foregoing and related ends, one or more aspects include the features fully described below and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail some illustrative features of one or more aspects. However, these features are merely indicative of some of the various ways in which the principles of the various aspects may be employed, and this specification is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a diagram illustrating an example of a wireless communication system and an access network.

[0012] Figure 2A is a diagram illustrating an example of a first frame according to various aspects of the present disclosure.

[0013] Figure 2B is a diagram illustrating an example of DL channels within a subframe according to various aspects of the present disclosure.

[0014] Figure 2C is a diagram illustrating an example of a second frame according to various aspects of the present disclosure.

[0015] Figure 2D is a diagram illustrating an example of UL channels within a subframe according to various aspects of the present disclosure.

[0016] Figure 3 is a diagram illustrating an example of a base station and a user equipment (UE) in an access network.

[0017] Figure 4 is a diagram illustrating examples of an anchor carrier, a secondary carrier, and a non-SSB secondary carrier.

[0018] Figure 5 is a diagram illustrating an example of an A-TRS burst including an A-TRS used in fast secondary cell (SCell) activation.

[0019] Figure 6 is a diagram illustrating an example of inter-band carrier aggregation deployment, in which a base station can communicate with a UE through different frequency bands in an anchor cell and a non-SSB secondary cell.

[0020] Figure 7 is a diagram illustrating an example of a timeline for A-TRS request and transmission in an anchor cell and a SSB-free secondary cell, respectively.

[0021] Figure 8 is a diagram illustrating an example of a multi-burst A-TRS configuration based on parameters indicated by a UE to a base station in an A-TRS request.

[0022] Fig. 9 is a diagram illustrating an example of a call flow between a UE and a base station.

[0023] Fig.10 is a flow chart of a method of performing wireless communication at a UE.

[0024] Fig.11 is a flow chart of a method of performing wireless communications at a base station.

[0025] Fig.12 is a diagram illustrating an example of a hardware implementation of an example apparatus.

[0026] Fig.13 is a diagram illustrating another example of a hardware implementation for another example apparatus. DETAILED DESCRIPTION

[0027] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. In order to provide a thorough understanding of the various concepts, the specific embodiments include specific details. However, it is apparent to those skilled in the art that these concepts may be practiced without these specific details. In some cases, well-known structures and components are shown in block diagram form to avoid obscuring such concepts.

[0028] In order to assist the UE in synchronizing with the base station during initial access, the base station may periodically send a synchronization signal block (SSB) to the UE. However, such periodic transmission of SSBs may inefficiently consume energy at the base station. For example, a base station that intends to serve a UE in multiple cells (including an anchor cell (e.g., PCell or primary component carrier) and a secondary cell (e.g., SCell or secondary component carrier)) through carrier aggregation (CA) typically periodically sends SBSs in both component carriers, even though the UE or base station may not intend to send or receive data in the secondary cell. Therefore, in order to save network energy in a multi-carrier scenario, the base station may suppress the transmission of SSBs (and other common channels and signals) in the secondary cell (or other component carrier). These secondary cells that lack SSBs are referred to as SSB-free secondary cells (or component carriers) throughout the disclosure.

[0029] However, when the base station implements an SSB-free secondary cell in inter-band CA for network energy saving, the lack of SSB transmission in such a secondary cell may affect the reception performance of the UE that intends to receive data in the secondary cell. For example, the UE's receiver typically applies an automatic gain control (AGC) loop and a time and / or frequency tracking loop (e.g., a phase-locked loop and / or a frequency-locked loop) to align or synchronize the voltage and waveform of the received signal, respectively. For example, these loops can be implemented in a receiver using hardware components (such as detectors, filters, oscillators, etc.). Using these loops (e.g., by performing the aforementioned loop operations), the UE can receive SSBs in the cell, and perform radio resource management (RRM) measurements of the SSBs for cell selection / reselection, SCell activation, beam management, or other functions. Due to the loop operations performed on these SBSs in the cell, the UE can then successfully receive subsequent downlink signals in the PDCCH or PDSCH of the cell. However, if such a cell lacks such an SSB (the cell is an SSB-free secondary cell), these loop operations may not be performed in the secondary cell before receiving the PDCCH or PDSCH, and thus the possibility of successfully receiving a downlink signal may be reduced.

[0030] The above-mentioned impact of the SSB-free secondary cell on the UE reception performance is specific to inter-band CA deployment. In contrast, in intra-band CA, the impact is negligible because the results of the loop operations (e.g., power alignment or waveform synchronization) that the UE has applied to the AGC and time / frequency tracking of the anchor carrier can be carried to the secondary carrier. For example, in intra-band CA, the propagation characteristics (e.g., power, frequency, and timing) of the downlink signal in the anchor carrier can be the same (or almost the same) as those in the secondary carrier, and thus the UE can leave the results of the loop operations performed on the SSB received in the anchor cell to the PDCCH and PDSCH signals received in the SSB-free secondary cell. However, in inter-band CA, the propagation characteristics of the anchor carrier and the SSB-free secondary carrier with respect to path loss, multipath fading, and Doppler effect may be different, and thus the UE may not simply leave the results of the loop operations performed in the anchor cell to the secondary cell in inter-band CA. Instead, the UE may be required to perform a separate loop operation in the secondary cell to achieve power alignment or waveform synchronization before receiving the PDCCH or PDSCH in the cell. However, since the secondary cell does not include SSB transmission (the cell is an SSB-free secondary cell), the UE cannot rely on the SSB in the secondary cell to perform these loop operations, and therefore the loop operation may end without being performed.

[0031] Therefore, in inter-band CA, the base station may not be able to use the SSB-free secondary cell for network energy saving unless different reference signals can be sent in the secondary cell for the UE to apply in the loop operation. Therefore, for this purpose, various aspects of the present disclosure provide that if the base station intends to schedule the PDSCH in the SSB-free secondary cell, the base station may send a tracking reference signal (TRS) (e.g., a CSI-RS for time / frequency tracking) in the SSB-free secondary cell for the UE to apply in its SCell loop operation before sending the PDSCH. For the purpose of using the SSB-free secondary cell for network energy saving, the base station may specifically utilize aperiodic TRS (A-TRS) to minimize the number of TRS transmissions and thus minimize power consumption. For example, the base station may send multiple bursts of A-TRS (also referred to as multi-burst A-TRS) in the SSB-free secondary cell for the UE to apply in its AGC loop and time / frequency tracking loop before receiving the PDCCH or PDSCH in the secondary cell.

[0032] One example where the base station may apply such an A-TRS is in fast SCell activation. In fast SCell activation, the base station may trigger one or two bursts of A-TRS (or temporary RS), where each burst includes two slots and four CSI-RS resources (two CSI-RS resources per slot) for the UE to apply for AGC or time / frequency tracking in the activated SCell. Therefore, before receiving the PDSCH in the SSB-free secondary cell, the base station may perform fast SCell activation of the SSB-free secondary cell using A-TRS that the UE may apply in its SCell loop operation. However, in such scenarios where the UE receives A-TRS in a SSB-free carrier, it would be helpful to specify a preferred A-TRS configuration for such A-TRS.

[0033] Therefore, various aspects of the present disclosure allow a UE to request (e.g., via UE assistance information) a base station to provide an A-TRS configuration indicating various parameters of an A-TRS that the base station will send in an SSB-free secondary cell, and allow the base station to control the transmission of the A-TRS in the SSB-free secondary cell based on a timer derived from the request. In addition, various aspects of the present disclosure allow the base station to trigger the transmission of the A-TRS in the SSB-free secondary cell via cross-carrier scheduling (e.g., using a DCI in an anchor cell that triggers the A-TRS in the SSB-free secondary cell) before the start of the timer or after the expiration of the timer derived from the request. In addition, various aspects of the present disclosure allow the base station to trigger the transmission of the A-TRS in the SSB-free secondary cell via self-scheduling (e.g., using a DCI in an SSB-free secondary cell that triggers the A-TRS and schedules the PDSCH in the SSB-free secondary cell) before the expiration of the timer derived from the request. Therefore, the network energy savings provided by the SSB-free secondary cell can be accommodated in inter-band CA.

[0034] Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as "elements"). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0035] As an example, an element, or any part of an element, or any combination of elements can be implemented as a "processing system", which includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on chip (SoCs), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gating logic, discrete hardware circuits, and other suitable hardware configured to perform various functionalities described throughout the present disclosure. One or more processors in a processing system can execute software. Whether it is referred to as software, firmware, middleware, microcode, hardware description language, or other names, software should be widely interpreted as meaning instructions, instruction sets, codes, code segments, program codes, programs, subroutines, software components, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, processes, functions, etc.

[0036] Therefore, in one or more example embodiments, the described functions can be implemented with hardware, software or any combination thereof. If implemented in software, the function can be stored or encoded on a computer-readable medium as one or more instructions or codes. Computer-readable media include computer storage media. Storage media can be any available medium that can be accessed by a computer. By way of example and not limitation, such computer-readable media can include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage device, magnetic disk storage device, other magnetic storage devices, a combination of computer-readable media of the above type, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

[0037] Figure 1 1 is a diagram illustrating an example of a wireless communication system and access network 100. The wireless communication system (also referred to as a wireless wide area network (WWAN)) includes a base station 102, a user equipment (UE) 104, an evolved packet core (EPC) 160, and another core network 190 (e.g., a 5G core (5GC)). The base station 102 may include a macro cell (a high-power cellular base station) and / or a small cell (a low-power cellular base station). A macro cell includes a base station. A small cell includes a femto cell, a pico cell, and a micro cell.

[0038] The base station 102 configured for 4G Long Term Evolution (LTE) (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) can interface with the EPC 160 via a first backhaul link 132 (e.g., an S1 interface). The base station 102 configured for 5G New Radio (NR) (collectively referred to as Next Generation RAN (NG-RAN)) can interface with the core network 190 via a second backhaul link 184. Among other functions, the base station 102 can also perform one or more of the following functions: delivery of user data, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment tracking, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 may communicate with each other directly or indirectly (eg, via the EPC 160 or the core network 190) via the third backhaul link 134 (eg, an X2 interface). The first backhaul link 132, the second backhaul link 184, and the third backhaul link 134 may be wired or wireless.

[0039] Base station 102 can communicate wirelessly with UE 104. Each of base stations 102 can provide communication coverage for a corresponding geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, a small cell 102' may have a coverage area 110' that overlaps with the coverage area 110 of one or more macro base stations 102. A network including both small cells and macro cells may be referred to as a heterogeneous network. A heterogeneous network may also include a home evolved Node B (eNB) (HeNB), which may provide services to a restricted group referred to as a closed subscriber group (CSG). A communication link 120 between base station 102 and UE 104 may include an uplink (UL) (also referred to as a reverse link) transmission from UE 104 to base station 102 and / or a downlink (DL) (also referred to as a forward link) transmission from base station 102 to UE 104. The communication link 120 may use multiple input multiple output (MIMO) antenna technology, including spatial multiplexing, beamforming and / or transmit diversity. The communication link may be through one or more carriers. For each carrier allocated in the carrier aggregation for up to a total of up to Yx MHz (x component carriers) for transmission in each direction, the base station 102 / UE 104 may use spectrum with a bandwidth of up to Y megahertz (MHz) (e.g., 5 MHz, 10 MHz, 15 MHz, 20 MHz, 100 MHz, 400 MHz, etc.). These carriers may or may not be adjacent to each other. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL ​​compared to UL). The component carrier may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as a primary cell (PCell) and the secondary component carrier may be referred to as a secondary cell (SCell).

[0040] Some UEs 104 may communicate with each other using a device-to-device (D2D) communication link 158. The D2D communication link 158 may use DL / UL WWAN spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication may be through a variety of wireless D2D communication systems, such as, for example, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, LTE, or NR.

[0041] The wireless communication system may also include a Wi-Fi access point (AP) 150 that communicates with a Wi-Fi station (STA) 152 via a communication link 154 in, for example, a 5 gigahertz (GHz) unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a clear channel assessment (CCA) to determine whether a channel is available prior to communication.

[0042] The small cell 102' may operate in licensed and / or unlicensed spectrum. When operating in an unlicensed spectrum, the small cell 102' may employ NR and use the same unlicensed spectrum (e.g., 5 GHz, etc.) as used by the Wi-Fi AP 150. The small cell 102' employing NR in the unlicensed spectrum may improve the coverage of the access network and / or increase the capacity of the access network.

[0043] The electromagnetic spectrum is typically subdivided into various categories, bands, channels, etc. based on frequency / wavelength. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz-7.125 GHz) and FR2 (24.25 GHz-52.6 GHz). Frequencies between FR1 and FR2 are typically referred to as mid-band frequencies. Although a portion of FR1 is greater than 6 GHz, FR1 is typically (interchangeably) referred to as the "sub-6 GHz" band in various documents and articles. A similar naming issue sometimes occurs with respect to FR2, which is typically (interchangeably) referred to as the "millimeter wave" band in documents and articles, although different from the extremely high frequency (EHF) band (30 GHz-300 GHz) identified as the "millimeter wave" band by the International Telecommunication Union (ITU).

[0044] In view of the above aspects, unless otherwise specifically stated, it should be understood that if used in this article, the term "below 6 GHz" or the like can broadly represent frequencies that can be less than 6 GHz, can be within FR1, or can include mid-band frequencies. In addition, unless otherwise specifically stated, it should be understood that if the term "millimeter wave" or the like is used in this article, it can broadly represent frequencies that can include mid-band frequencies, can be within FR2, or can be within the EHF band.

[0045] The base station 102, whether a small cell 102' or a large cell (e.g., a macro base station), may include and / or be referred to as an eNB, a gNodeB (gNB), or another type of base station. Some base stations, such as gNB 180, may operate in the traditional sub-6 GHz spectrum, in millimeter wave frequencies, and / or near millimeter wave frequencies to communicate with the UE 104. When the gNB 180 operates in millimeter wave or near millimeter wave frequencies, the gNB 180 may be referred to as a millimeter wave base station. The millimeter wave base station 180 may utilize beamforming 182 with the UE 104 to compensate for path loss and short range. The base station 180 and the UE 104 may each include multiple antennas, such as antenna elements, antenna panels, and / or antenna arrays, to facilitate beamforming.

[0046] Base station 180 may transmit beamformed signals in one or more transmit directions 182' to UE 104. UE 104 may receive beamformed signals from base station 180 in one or more receive directions 182". UE 104 may also transmit beamformed signals to base station 180 in one or more transmit directions. Base station 180 may receive beamformed signals from UE 104 in one or more receive directions. Base station 180 / UE 104 may perform beam training to determine the best receive direction and transmit direction for each of base station 180 / UE 104. The transmit direction and receive direction of base station 180 may be the same or may be different. The transmit direction and receive direction of UE 104 may be the same or may be different.

[0047] The EPC 160 may include a mobility management entity (MME) 162, other MMEs 164, a serving gateway 166, an MBMS gateway 168, a broadcast multicast service center (BM-SC) 170, and a packet data network (PDN) gateway 172. The MME 162 may communicate with a home subscriber server (HSS) 174. The MME 162 is a control node that handles signaling between the UE 104 and the EPC 160. Generally speaking, the MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are passed through the serving gateway 166, which itself is connected to the PDN gateway 172. The PDN gateway 172 provides UE IP address allocation and other functions. The PDN gateway 172 and the BM-SC 170 are connected to IP services 176. The IP services 176 may include the Internet, an intranet, an IP multimedia subsystem (IMS), a PS streaming service, and / or other IP services. The BM-SC 170 may provide functions for MBMS user service configuration and delivery. BM-SC 170 may serve as an entry point for content provider MBMS delivery, may be used to authorize and initiate MBMS bearer services in a public land mobile network (PLMN), and may be used to schedule MBMS delivery. MBMS gateway 168 may be used to distribute MBMS services to base stations 102 belonging to a multicast broadcast single frequency network (MBSFN) area of ​​a broadcast specific service, and may be responsible for session management (start / stop) and for collecting eMBMS related billing information.

[0048] The core network 190 may include an access and mobility management function (AMF) 192, other AMFs 193, a session management function (SMF) 194, and a user plane function (UPF) 195. The AMF 192 may communicate with a unified data management (UDM) 196. The AMF 192 is a control node that handles signaling between the UE 104 and the core network 190. Typically, the AMF 192 provides quality of service (QoS) flows and session management. All user IP packets are delivered through the UPF 195. The UPF 195 provides UE IP address allocation and other functions. The UPF 195 is connected to an IP service 197. The IP service 197 may include the Internet, an intranet, an IMS, a packet switching (PS) streaming media service, and / or other IP services.

[0049] Base stations may include and / or be referred to as gNBs, Node Bs, eNBs, access points, base transceivers, radio base stations, radio transceivers, transceiver functions, basic service sets (BSSs), extended service sets (ESSs), transmit receive points (TRPs), or some other suitable terminology. Base stations 102 provide access points to EPC 160 or core network 190 for UEs 104. Examples of UEs 104 include cellular phones, smart phones, session initiation protocol (SIP) phones, laptops, personal digital assistants (PDAs), satellite radios, global positioning systems, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, tablets, smart devices, wearable devices, vehicles, electric meters, gas pumps, large or small kitchen appliances, healthcare devices, implants, sensors / actuators, displays, or any other similarly functional devices. Some of the UEs 104 may be referred to as IoT devices (e.g., parking meters, gas pumps, toasters, vehicles, heart monitors, etc.). UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

[0050] Although the present disclosure may focus on 5G NR, the concepts and aspects described herein may be applicable to other similar areas such as LTE, Advanced LTE (LTE-A), Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), and / or other wireless / radio access technologies.

[0051] Refer again Figure 1 In certain aspects, the UE 104 may include an A-TRS receiving component 198 configured to: send a request for an aperiodic tracking reference signal (A-TRS) in a first cell; and receive the A-TRS in a second cell in the absence of a synchronization signal block (SSB) transmission based on the request.

[0052] Refer again Figure 1 In certain aspects, the base station 102 / 180 may include an A-TRS transmission component 199 configured to: receive a request for an A-TRS in a first cell; and transmit the A-TRS in a second cell in the absence of SSB transmission based on the request.

[0053] Figure 2A FIG200 is a diagram illustrating an example of a first subframe within a 5G NR frame structure. Figure 2BFIG230 is a diagram illustrating an example of DL channels within a 5G NR subframe. Figure 2C FIG250 is a diagram illustrating an example of a second subframe within a 5G NR frame structure. Figure 2D FIG280 is a diagram illustrating an example of an UL channel within a 5G NR subframe. The 5G NR frame structure may be frequency division duplex (FDD) (wherein for a particular set of subcarriers (carrier system bandwidth), a subframe within the subcarrier set is dedicated to either DL or UL), or may be time division duplex (TDD) (wherein for a particular set of subcarriers (carrier system bandwidth), a subframe within the subcarrier set is dedicated to both DL and UL). Figure 2A , Figure 2C In the example provided, the 5G NR frame structure is assumed to be TDD, where subframe 4 is configured with slot format 28 (most of which are DL), where D is DL, U is UL, and F is flexible between DL / UL, and subframe 3 is configured with slot format 34 (most of which are UL). Although subframes 3 and 4 are shown as having slot formats 34 and 28, respectively, any particular subframe may be configured with any of the various available slot formats 0-61. Slot formats 0 and 1 are full DL and full UL, respectively. Other slot formats 2-61 include a mix of DL, UL and flexible symbols. The UE is configured with the slot format through the received slot format indicator (SFI) (dynamically configured through DL control information (DCI) or semi-statically / statically configured through radio resource control (RRC) signaling). Note that the following description also applies to the 5G NR frame structure as TDD.

[0054] Other wireless communication technologies may have different frame structures and / or different channels. For example, a 10 millisecond (ms) frame may be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. A subframe may also include a microslot, which may include 7, 4, or 2 symbols. Each time slot may include 7 or 14 symbols, depending on the time slot configuration. For time slot configuration 0, each time slot may include 14 symbols, and for time slot configuration 1, each time slot may include 7 symbols. The symbol on the DL may be a cyclic prefix (CP) orthogonal frequency division multiplexing (OFDM) (CP-OFDM) symbol. The symbol on the UL may be a CP-OFDM symbol (for high throughput scenarios) or a discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbol (also known as a single carrier frequency division multiple access (SC-FDMA) symbol) (for power-constrained scenarios; limited to single-stream transmission). The number of time slots in a subframe is based on the time slot configuration and parameter set (numerology). For slot configuration 0, different parameter sets μ0 to 4 allow 1, 2, 4, 8, and 16 slots per subframe, respectively. For slot configuration 1, different parameter sets 0 to 2 allow 2, 4, and 8 slots per subframe, respectively. Accordingly, for slot configuration 0 and parameter set μ, there are 14 symbols per slot and 2 per subframe. μ time slots. The subcarrier spacing and symbol length / duration are functions of the parameter set. The subcarrier spacing can be equal to 2 μ *15 kilohertz (kHz), where μ is parameter set 0 to 4. Therefore, the subcarrier spacing for parameter set μ=0 is 15 kHz, and the subcarrier spacing for parameter set μ=4 is 240 kHz. The symbol length / duration is inversely related to the subcarrier spacing. FIG. 2A to FIG. 2D An example is provided for slot configuration 0 with 14 symbols per slot and parameter set μ=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 μs. Within a frame set, there may be one or more different bandwidth parts (BWPs) that are frequency-division multiplexed (see Figure 2B ). Each BWP can have a specific set of parameters.

[0055] A resource grid may be used to represent the frame structure. Each slot includes a resource block (RB) (also referred to as a physical RB (PRB)) extending over 12 consecutive subcarriers. The resource grid is divided into a number of resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0056] like Figure 2AAs illustrated, some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include a demodulation RS (DM-RS) for channel estimation at the UE (indicated as R for a particular configuration). x , where 100x is the port number, but other DM-RS configurations are possible) and a channel state information reference signal (CSI-RS). RS may also include beam measurement RS (BRS), beam refinement RS (BRRS) and phase tracking RS (PT-RS).

[0057] Figure 2B Examples of various DL channels within a subframe of a frame are illustrated. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in an OFDM symbol. The PDCCH within a BWP may be referred to as a control resource set (CORESET). Additional BWPs may be located at higher and / or lower frequencies on the channel bandwidth. The primary synchronization signal (PSS) may be within symbol 2 of a specific subframe of a frame. The PSS is used by UE 104 to determine subframe / symbol timing and physical layer identification. The secondary synchronization signal (SSS) may be within symbol 4 of a specific subframe of a frame. The SSS is used by the UE to determine the physical layer cell identification group number and radio frame timing. Based on the physical layer identification and the physical layer cell identification group number, the UE may determine the physical cell identifier (PCI). Based on the PCI, the UE may determine the position of the aforementioned DM-RS. The physical broadcast channel (PBCH) carrying the master information block (MIB) can be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block (also referred to as an SS block (SSB)). The MIB provides the system frame number (SFN) and the number of RBs in the system bandwidth. The physical downlink shared channel (PDSCH) carries user data, broadcast system information not sent over the PBCH (such as the system information block (SIB)), and paging messages.

[0058] like Figure 2CAs illustrated, some of the REs carry DM-RS (indicated as R for a particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE may send a DM-RS for a physical uplink control channel (PUCCH) and a DM-RS for a physical uplink shared channel (PUSCH). The PUSCH DM-RS may be sent in the first or first two symbols of the PUSCH. Depending on whether a short PUCCH or a long PUCCH is sent and depending on the specific PUCCH format used, the PUCCH DM-RS may be sent in different configurations. The UE may send a sounding reference signal (SRS). The SRS may be sent in the last symbol of a subframe. The SRS may have a comb structure, and the UE may send the SRS on one of the comb structures in the comb structure. The SRS may be used by the base station for channel quality estimation to achieve frequency-dependent scheduling of the UL.

[0059] Figure 2D Examples of various UL channels within a subframe of a frame are illustrated. The PUCCH may be located at a position as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, channel quality indicator (CQI), precoding matrix indicator (PMI), rank indicator (RI), and hybrid automatic repeat request (HARQ) acknowledgement (ACK) / negative acknowledgement (NACK) feedback. The PUSCH carries data and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and / or UCI.

[0060] Figure 33 is a block diagram of a base station 310 in an access network communicating with a UE 350. In the DL, IP packets from the EPC 160 may be provided to the controller / processor 375. The controller / processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression / decompression, security (encryption, decryption, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with delivery of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0061] The transmit (TX) processor 316 and receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1 (which includes the physical (PHY) layer) may include error detection on the transport channel, forward error correction (FEC) coding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The TX processor 316 handles the mapping to the signal constellation based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-order phase shift keying (M-PSK), M-order quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be separated into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and / or frequency domain, and then combined together using an inverse fast Fourier transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially pre-coded to generate multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation schemes, as well as for spatial processing. Channel estimates may be derived from reference signals and / or channel state feedback sent by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with a corresponding spatial stream for transmission.

[0062] At the UE 350, each receiver 354RX receives a signal through its corresponding antenna 352. Each receiver 354RX recovers the information modulated onto the RF carrier and provides the information to a receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial stream destined for the UE 350. If multiple spatial streams are destined for the UE 350, they can be combined into a single OFDM symbol stream by the RX processor 356. The RX processor 356 then converts the OFDM symbol stream from the time domain to the frequency domain using a fast Fourier transform (FFT). The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier and the reference signal are recovered and demodulated by determining the most likely signal constellation point sent by the base station 310. These soft decisions can be based on channel estimates calculated by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals originally sent on the physical channel by base station 310. The data and control signals are then provided to controller / processor 359, which implements layer 3 and layer 2 functionality.

[0063] The controller / processor 359 may be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller / processor 359 is also responsible for error detection using an ACK and / or NACK protocol to support HARQ operations.

[0064] Similar to the functionality described in conjunction with DL transmissions performed by the base station 310, the controller / processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functionality associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functionality associated with delivery of upper layer PDUs, error correction through ARQ, concatenation, segmentation and reassembly of RLC SDUs, resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

[0065] Channel estimates derived by the channel estimator 358 based on a reference signal or feedback sent by the base station 310 may be used by the TX processor 368 to select the appropriate coding and modulation schemes and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a corresponding spatial stream for transmission.

[0066] UL transmissions are processed at the base station 310 in a manner similar to that described in conjunction with the receiver functionality at the UE 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

[0067] The controller / processor 375 may be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport channels and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover IP packets from the UE 350. The IP packets from the controller / processor 375 may be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using ACK and / or NACK protocols to support HARQ operations.

[0068] At least one of the TX processor 368, the RX processor 356, and the controller / processor 359 may be configured to combine Figure 1 The A-TRS receiving component 198 is used to perform various aspects.

[0069] At least one of the TX processor 316, the RX processor 370, and the controller / processor 375 may be configured to combine Figure 1 The A-TRS transmission component 199 performs various aspects.

[0070] In carrier aggregation (CA), two or more component carriers (CCs) may be aggregated to support a wider transmission bandwidth. Aggregation may be arranged using contiguous CCs within the same operating band (e.g., intra-band contiguous CA), using non-contiguous CCs within the same operating band but with gaps therebetween (e.g., intra-band non-contiguous CA), and using CCs within different operating bands (e.g., inter-band CA). In DL carrier aggregation, a base station transmits downlink data to a UE in multiple CCs, while in UL carrier aggregation, a UE transmits uplink data to a base station in multiple CCs.

[0071] In order to assist the UE in synchronizing with the base station during initial access, the base station may periodically send SSBs to the UE. However, such periodic transmission of SSBs may inefficiently consume energy at the base station. For example, a base station that intends to serve a UE in multiple cells (including an anchor cell (e.g., PCell or primary component carrier) and a secondary cell (e.g., SCell or secondary component carrier)) through CA typically sends SBSs periodically in two CCs, even though the UE or base station may not intend to send or receive data in the secondary cell. Therefore, in order to save network energy in multi-carrier scenarios, the base station may suppress the transmission of SSBs (and other common channels and signals) in the secondary cell (or other CCs). These secondary cells that lack SSBs are referred to as SSB-free secondary cells (or CCs) throughout the disclosure.

[0072] Figure 4 An example 400 of an anchor carrier 402 (e.g., PCell), a secondary carrier 404, and a SSB-free secondary carrier 406 is illustrated. In order to perform downlink and uplink synchronization with the base station, the UE may periodically receive SSB 408 (or discovery reference signal (DRS)) and system information (SI) 410 (e.g., including various configurations of SIBs for network operation) in the anchor carrier 402. The base station may periodically send SSB 408 and SI 410 in the anchor carrier 402 even when the UE does not intend to receive or send data to the base station. However, in the secondary carriers 404, 406, the base station may perform network energy saving by eliminating the transmission of one or more of these signals. Therefore, Figure 4These secondary carriers are referred to as Energy Saving (ES) component carriers (CCs). For example, to save energy in the secondary carrier 404 when no downlink data is pending for the UE, the base station may refrain from periodically sending SI 410 because this information is already sent in the anchor carrier 402, although the base station may continue to send SBS 408 (or DRS) in the secondary carrier 404. Furthermore, to save additional energy in the SSB-free secondary carrier 406 when no downlink data is pending for the UE, the base station may further refrain from periodically sending SSB 408 (and SI 410) because this information is already sent in the anchor carrier 402.

[0073] However, when the base station implements an SSB-free secondary cell in inter-band CA for network energy saving, the lack of SSB transmission in such a secondary cell may affect the reception performance of the UE that intends to receive data in the secondary cell. For example, the UE's receiver typically applies an automatic gain control (AGC) loop and a time and / or frequency tracking loop (e.g., a phase-locked loop and / or a frequency-locked loop) to align or synchronize the voltage and waveform of the received signal, respectively. For example, these loops can be implemented in a receiver using hardware components (such as detectors, filters, oscillators, etc.). Using these loops (e.g., by performing the aforementioned loop operations), the UE can receive SSBs in the cell, and perform radio resource management (RRM) measurements of the SSBs for cell selection / reselection, SCell activation, beam management, or other functions. Due to the loop operations performed on these SBSs in the cell, the UE can then successfully receive subsequent downlink signals in the PDCCH or PDSCH of the cell. However, if such a cell lacks such an SSB (the cell is an SSB-free secondary cell), these loop operations may not be performed in the secondary cell before receiving the PDCCH or PDSCH, and thus the possibility of successfully receiving a downlink signal may be reduced.

[0074] The above-mentioned impact of the SSB-free secondary cell on the UE reception performance is specific to inter-band CA deployment. In contrast, in intra-band CA, the impact is negligible because the results of the loop operations (e.g., power alignment or waveform synchronization) that the UE has applied to the AGC and time / frequency tracking of the anchor carrier can be carried to the secondary carrier. For example, in intra-band CA, the anchor carrier and the secondary carrier are usually located in the same frequency band, and in many cases can be adjacent carriers for the same base station (intra-band continuous CA). These cells can also be co-located. Therefore, the propagation characteristics (e.g., power, frequency, and timing) of the downlink signal in the anchor carrier can be the same (or almost the same) as those in the secondary carrier, and therefore the UE can leave the results of the loop operations performed on the SSB received in the anchor cell to the PDCCH and PDSCH signals received in the SSB-free secondary cell. However, in inter-band CA, the anchor carrier and the SSB-free secondary carrier are in different frequency bands (e.g., 2 GHz band and 3 GHz band, respectively), and thus their propagation characteristics with respect to path loss, multipath fading, Doppler effect, etc. may be different, even if the anchor cell and the SCell are co-located. Therefore, the UE may not simply leave the result of the loop operation performed in the anchor cell to the secondary cell in inter-band CA; instead, the UE may be required to perform a separate loop operation in the secondary cell to achieve power alignment or waveform synchronization before receiving the PDCCH or PDSCH in the cell. However, since the secondary cell does not include SSB transmission (the cell is an SSB-free secondary cell), the UE cannot rely on the SSB in the secondary cell to perform these loop operations, and thus the loop operation may end without being performed before the PDCCH or PDSCH is transmitted.

[0075] Therefore, in inter-band CA, the base station may not be able to use the SSB-free secondary cell for network energy saving unless a different reference signal can be sent in the secondary cell for the UE to apply in the loop operation. Therefore, for this purpose, various aspects of the present disclosure provide that if the base station intends to schedule the PDSCH in the SSB-free secondary cell, the base station may send a tracking reference signal (TRS) (e.g., CSI-RS for time / frequency tracking) in the SSB-free secondary cell for the UE to apply in its SCell loop operation before sending the PDSCH. Typically, the base station may send TRS periodically (e.g., P-TRS), semi-persistently (e.g., SP-TRS), or aperiodically (A-TRS), but here, for the purpose of using the SSB-free secondary cell for network energy saving, the base station may specifically utilize A-TRS to minimize the number of TRS transmissions and therefore minimize power consumption. For example, the base station may send multiple bursts of A-TRS (also referred to as multi-burst A-TRS) in a secondary cell without SSB for the UE to apply in its AGC loop and time / frequency tracking loop before receiving PDCCH or PDSCH in the secondary cell.

[0076] An example where the base station may apply such an A-TRS is in fast SCell activation. In fast SCell activation, the base station may trigger one or two bursts of A-TRS (or temporary RS), where each burst includes two slots and four CSI-RS resources (two CSI-RS resources per slot) for the UE to apply to AGC or time / frequency tracking in an activated SCell that is known and belongs to frequency range 1 (FR1), unknown and belongs to FR1, or belongs to frequency range (FR2). For example, in a known SCell that belongs to FR1, if the SCell measurement period is equal to or less than a given time period (e.g., 2400ms), one burst may be applied to time / frequency tracking, and if the SCell measurement period is greater than the given time period (e.g., 2400ms), one burst may be applied to AGC and a separate burst may be applied to time / frequency tracking. In the latter case, the minimum gap between the RS symbols for AGC and the RS symbols for time / frequency acquisition can be a number of slots (e.g., 2 slots) for one subcarrier spacing (e.g., 15kHz or 30kHz) and another number of slots (e.g., 3 slots) for another subcarrier spacing (e.g., 60kHz). In an unknown SCell belonging to FR1, one burst may be applied for time-frequency tracking. In addition, if the power difference in the serving cell and the SCell to be activated is less than or equal to a threshold (e.g., 6dB), another burst may be applied to AGC in a SCell that is continuous with an active serving cell in the same band (intra-band continuous CA). In an SCell belonging to FR2, if at least one active serving cell on the FR2 band and a temporary RS for the target SCell are provided, or if there is no active serving cell on the FR2 band and the SCell to be activated is known to the UE, one burst may be applied to time-frequency tracking. However, if the activated SCell is unknown to the UE and there is no active serving cell on the FR2 band, the Temporary RS is not available for AGC (although it may or may not be available for time / frequency tracking).

[0077] Figure 5An example 500 of an A-TRS burst 502 including an A-TRS 504 used in fast SCell activation is illustrated. In order to speed up the activation of the SCell from the deactivated state, the base station may send an A-TRS 504, and the UE may perform the aforementioned loop operation on it in the SCell. In the illustrated example, two A-TRS bursts are shown, each consisting of two time slots and four symbols carrying the A-TRS. For example, the first A-TRS burst may be used for AGC initialization and the second A-TRS burst may be used for frequency and time tracking. Depending on the deployment scenario (e.g., whether the SCell is known and belongs to FR1, is unknown and belongs to FR1, or belongs to F2), the base station may send one or two A-TRS bursts for loop operation. If multiple A-TRS bursts are sent, there may be a gap between the two bursts (e.g., based on UE capabilities and network configuration).

[0078] Figure 6 An example 600 of an inter-band CA deployment is illustrated, where a base station can communicate with a UE over different frequency bands in an anchor cell 602 and a non-SSB secondary cell 604. In the anchor cell 602, the base station can send SSB 606, A-TRS 608, PDCCH 610, and PDSCH 612 to the UE, and receive corresponding uplink transmissions (e.g., RACH, PUSCH, PUCCH, etc.) from the UE without performing network energy saving. In the non-SSB secondary cell 604, the base station can also send A-TRS 614 during fast cell activation of the non-SSB secondary cell 604 for network energy saving. The UE can measure the A-TRS 614 in the non-SSB secondary cell 604 to align or synchronize its AGC loop and time / frequency tracking loop when performing its loop operation. Later, when the base station intends to send downlink data to the UE in the non-SSB secondary cell 604, the base station may send downlink data intended for the UE in the PDSCH 616 in the non-SSB secondary cell 604. Since the UE has performed AGC and time / frequency synchronization using the A-TRS 614, the UE may receive the scheduled PDSCH in the secondary cell.

[0079] Therefore, before receiving the PDSCH in the non-SSB secondary cell, the base station can use the A-TRS that the UE can apply in its SCell loop operation to perform fast SCell activation of the non-SSB secondary cell. However, in such scenarios where the UE receives A-TRS in the non-SSB carrier (such as in Figure 6), it would be helpful to specify a preferred A-TRS configuration for such A-TRS (e.g., A-TRS 614). Thus, aspects of the present disclosure allow a UE to request (e.g., via UE assistance information) a base station to provide an A-TRS configuration that indicates various parameters of the A-TRS that the base station will send in the SSB-free secondary cell, and allow the base station to control the transmission of the A-TRS in the SSB-free secondary cell based on a timer derived from the request. In addition, aspects of the present disclosure allow the base station to trigger the transmission of the A-TRS in the SSB-free secondary cell via cross-carrier scheduling (e.g., using a DCI in an anchor cell that triggers the A-TRS in the SSB-free secondary cell) before the start of the timer or after the expiration of the timer derived from the request. In addition, aspects of the present disclosure allow the base station to trigger the transmission of the A-TRS in the SSB-free secondary cell via self-scheduling (e.g., using a DCI in the SSB-free secondary cell that triggers the A-TRS and schedules the PDSCH in the SSB-free secondary cell) before the expiration of the timer derived from the request. Therefore, the network energy savings provided by the SSB-free secondary cell can be accommodated in inter-band CA.

[0080] Figure 7An example 700 of a timeline for A-TRS request and transmission in an anchor cell 702 and a non-SSB secondary cell 704, respectively, is illustrated. Initially, at block 706, the UE may send a request to the base station in the anchor cell 702 (e.g., via RRC signaling) to provide an A-TRS configuration that defines or indicates parameters for A-TRS in the non-SSB secondary cell 704. For example, when the UE establishes a connection to the anchor cell 702, the UE may provide the base station with UE assistance information for A-TRS transmission in the non-SSB secondary cell 704. In one example, the UE may send a request for multi-burst A-TRS in the anchor cell 702 via a MAC-CE or RRC message (e.g., UE assistance information signaling). The request may include parameters or information that the base station may use to configure the A-TRS. For example, one parameter that the UE may indicate in the request is a target secondary cell for A-TRS transmission (e.g., an index of the non-SSB secondary cell 704). For example, if the UE is connected to multiple secondary cells on different frequency bands or with different parameter sets, the A-TRS configuration may be different for different secondary cells, and thus the UE indicates via its index which secondary cell the A-TRS configuration will be applied to. Another parameter that the UE may indicate in the request is the TRS bandwidth (the bandwidth over which the A-TRS is sent). For example, depending on the loop operation that the UE is to perform in the SSB-free secondary cell, the UE may request the base station to send TRS over the entire bandwidth of the secondary cell or over a subset of the bandwidth of the secondary cell, and thus the UE may indicate this information in the request. Other parameters that the UE may indicate in its request include the number of time slots used for TRS bursts (e.g., one or two time slots per A-TRS burst), the number of TRS bursts (e.g., two TRS bursts), and the time slot gap between TRS bursts (e.g., two time slots between TRS bursts).

[0081] In response to receiving the request at block 706, at block 707, the base station may send a configuration of the A-TRS to the UE in the anchor cell 702 using the parameters indicated in the request (e.g., via RRC signaling). For example, the base station may send an RRC configuration at block 707 that configures a multi-burst A-TRS that the base station intends to send later in the SSB-free secondary cell 704. The A-TRS configuration may include, for example, a resource set configuration for the A-TRS (such as non-zero power), a channel state information reference signal (NZP-CSI-RS) resource set configuration for the multi-burst A-TRS, and an aperiodic channel state information (A-CSI-RS) trigger state configuration for the A-TRS. The NZP CSI-RS resource set configuration may include, for example, an NZP-CSI-RS resource set for one A-TRS burst, multiple A-TRS bursts in a transmission opportunity, and a time slot gap between A-TRS bursts.

[0082] Figure 8 This example illustrates a method based on a UE request in an A-TRS (eg, Figure 7 The multi-burst A-TRS configuration of the parameters indicated to the base station in the request at block 706 of Figure 7 800 of the configuration at block 707 of FIG. 800 . For example, the UE may request the number of TRS slots 802 for TRS bursts 804, the number of TRS bursts 804 to be sent by the base station in a transmit opportunity 805, and the number of interstitial slots 806 between TRS bursts 804. As an example, the UE may request an A-TRS configuration including two TRS slots 802 per TRS burst 804, two TRS bursts 804, and two interstitial slots 806. Thus, as Figure 8 As shown in the example of , the A-TRS configuration may include two TRS bursts 804 in an A-TRS transmission opportunity, two TRS time slots 802 per TRS burst 804, and two gap time slots 806 between TRS bursts 804. Alternatively, the UE may request an A-TRS configuration different from the illustrated configuration, such as a configuration including a different number of TRS time slots 802 per TRS burst 804, a different number of TRS bursts 804 per TRS opportunity, and / or a different number of gap time slots 806 between TRS bursts 804.

[0083] Return to reference Figure 7 , the request (e.g., UE assistance information) may include one or more parameters related to a timer 708, which is associated with a duration during which the base station can send A-TRS in the SSB-free secondary cell 704. For example, these parameters or timeline information may include a minimum time gap between A-TRS transmission opportunities in the SSB-free secondary cell 704, and a maximum time gap between the last burst of A-TRS transmission and a subsequent PDCCH / PDSCH transmission. Based on the timeline information provided by the UE, the base station may determine a length of time during which the base station can send A-TRS in the SSB-free secondary cell 704 (e.g., the value of timer 708), and a maximum time after determining the A-TRS that the base station can schedule or send PDSCH in the SSB-free secondary cell within this time length. For example, if the UE indicates that the minimum time gap between A-TRS transmission opportunities is 100 ms, the base station may send multi-burst A-TRS in the SSB-free secondary cell with a periodicity of not less than 100 ms (e.g., based on Figure 8 In addition, if the UE indicates that the maximum time gap between an A-TRS transmission and an associated PDSCH transmission is 200 ms, the base station may send PDCCH / PDSCH in the SSB-free secondary cell no later than 200 ms after sending an A-TRS in the SSB-free secondary cell (e.g., the last A-TRS burst in a multi-burst A-TRS transmission).

[0084] In addition, these parameters and therefore the value of the timer 708 or its periodicity may change depending on the current channel conditions of the UE (e.g., if the UE is stationary or mobile). For example, if the UE is stationary, the UE may request the base station to send the multi-burst A-TRS with a larger periodicity (e.g., 200ms), while if the UE is in a highly mobile situation, the UE may request the base station to send the multi-burst A-TRS with a smaller periodicity (e.g., 40ms). Therefore, through this request, the UE can dynamically instruct the base station to set different values ​​for the timer 708 based on the current channel conditions of the UE.

[0085] Thus, the UE may request (e.g., via UE assistance information signaling) in the anchor cell 702 that the base station provide A-TRS in the SSB-free secondary cell 704 according to the timer parameters indicated in the request. The anchor cell and the SSB-free secondary cell may be in different frequency bands. Due to the timer-controlled A-TRS, the UE may use its loop operation to achieve power alignment or waveform frequency / time synchronization in the SSB-free secondary cell, and the UE may receive downlink data in the SSB-free secondary cell accordingly. Thus, the network energy savings provided by the lack of SSB transmission in the SSB-free secondary cell may be accommodated in inter-band CA.

[0086] Initially, when the UE requests initial A-TRS transmission in the SSB-free secondary cell 704 after activation of the SSB-free secondary cell 704, or when the base station intends to provide A-TRS transmission in the SSB-free secondary cell 704 after an inactivity period in the SSB-free secondary cell 704 (e.g., after expiration of the timer 708), the base station may trigger A-TRS using cross-carrier scheduling at block 710. For example, the base station may send a DCI (PDCCH) in the anchor cell 702 that schedules A-TRS transmission in the SSB-free secondary cell 704. The trigger PDCCH may include parameters such as a secondary cell index for the SSB-free secondary cell 704 (the target SCell for cross-carrier scheduling) and an A-TRS triggering state. Here, at block 710, the base station transmits a trigger (e.g., DCI) in the anchor cell 702 rather than in the SSB-free secondary cell 704 where the A-TRS transmission itself occurs, because the UE may not yet have (or no longer have) reliable alignment or synchronization of power and waveform frequency / timing from its loop operation in the SSB-free secondary cell 704. Therefore, at this point at 710, the base station transmits a trigger for the A-TRS in the SSB-free secondary cell 704 using a cross-cell trigger in the anchor cell 702.

[0087] After the UE performs loop operation and thus obtains alignment or synchronization of power and waveform frequency / timing in the non-SSB secondary cell 704, the UE may receive the PDCCH and PDSCH in the non-SSB secondary cell 704. Thus, at block 712, after cross-cell triggering of the A-TRS, the base station may send the A-TRS to the UE in one or more bursts (e.g., based on information such as Figure 8 800 of example 700). For example, the base station may send the A-TRS in a burst including multiple time slots and then send the PDSCH to the UE in a subsequent time slot. At box 712, the base station may send the PDSCH no later than the requested maximum time gap after the A-TRS transmission at box 712. For example, if the maximum time gap indicated in the UE request is 200ms, then at box 712, the base station may send the PDSCH no later than 200ms after the last A-TRS burst sent at box 712. After the base station transmits the trigger at box 710 or transmits the A-TRS at box 712, the base station may set a timer 708 for A-TRS transmission in the SSB-free secondary cell 704. The timer 708 may be set based on at least the maximum time gap described previously.

[0088] After sending the downlink data to the UE at box 712, the base station may determine that there is still pending (or additional) downlink data intended for the UE. For example, the base station may determine to schedule a retransmission of previous data in the PDSCH or a new transmission of subsequent data via the transmission of DCI in the PDCCH. Alternatively or additionally, the PDSCH transmission at box 712 may be part of a downlink data burst that includes additional data to be transmitted to the UE. If the timer 708 is still running at this time (the timer has not expired), the alignment or synchronization of power and waveform frequency / timing previously achieved by the UE in its loop operation in the secondary cell may still be maintained, and therefore the base station may determine that the UE may still be able to successfully receive A-TRS and PDCCH / PDSCH in the SSB-free secondary cell 704.

[0089] Thus, while timer 708 is still running, at block 714, the base station may trigger a subsequent A-TRS and schedule a subsequent PDSCH using self-scheduling. Similarly, at block 716, due to self-scheduling, the base station may send a subsequent A-TRS in one or more bursts (e.g., based on information such as Figure 8) and subsequent downlink data in the PDSCH. For example, the base station may send a DCI (PDCCH) scheduling an A-TRS burst in the SSB-free secondary cell 704 at box 714, and send a PDSCH transmission in the same time slot in the same SSB-free secondary cell at box 716. At box 716, the base station may send the A-TRS burst no earlier than the requested minimum time gap after the A-TRS burst transmission at box 712. For example, if the minimum time gap indicated in the UE request is 100 ms, then at box 716, the base station may send the multi-burst A-TRS no earlier than 100 ms after the multi-burst A-TRS is sent at box 712. In addition, at box 716, the base station may send the PDSCH no later than the requested maximum time gap after the A-TRS transmission at box 716. For example, if the maximum time gap indicated in the UE request is 200 ms, then at block 716 the base station may send the PDSCH no later than 200 ms after the last A-TRS burst sent at block 716 .

[0090] At or near the time when the base station transmits the trigger at block 714 or transmits the A-TRS at block 716, the base station may also reset the timer 708 for A-TRS transmission in the SSB-free secondary cell 704. Thus, as long as there is still downlink data intended for the UE, the base station may continue (e.g., repeat) the operations of blocks 714 and 716 in the SSB-free secondary cell 704 while the timer 708 is running. During this time, similar to the previously described A-TRS transmissions, the corresponding subsequent A-TRS transmissions may be transmitted no earlier than a minimum time gap (e.g., 100 ms) after the corresponding immediately preceding A-TRS transmission. Similarly, the corresponding subsequent PDSCH transmissions may be transmitted no later than a maximum time gap (e.g., 200 ms) after the corresponding, immediately preceding, last A-TRS burst transmission.

[0091] Later, the base station may determine that there is no longer pending (or additional) downlink data remaining to be transmitted to the UE. For example, the PDSCH transmission at block 716 may be the end of a downlink data burst transmitted to the UE, and there may be no additional data intended for the UE in the SSB-free secondary cell 704 at this time. In response to this determination (e.g., there is no pending or ongoing downlink data transmission), the base station may prohibit or stop sending A-TRS in the SSB-free secondary cell 704. Therefore, timer 708 may expire. After the expiration of timer 708, the alignment or synchronization of power and waveform frequency / timing previously achieved by the UE in its loop operation in the secondary cell may no longer be maintained, and therefore the base station may determine that the UE may no longer be able to successfully receive A-TRS and PDCCH / PDSCH in the SSB-free secondary cell 704. For example, the lapse of time represented by timer 708 may result in misalignment or desynchronization of power and waveform frequency / timing.

[0092] Therefore, if after expiration of the timer 708, the base station intends to send downlink data to the UE again, the base station may repeat the aforementioned operations of the A-TRS trigger using cross-carrier scheduling at block 710. For example, the base station may again send DCI in the anchor cell 702, which triggers the A-TRS and schedules the PDSCH in the SSB-free secondary cell 704. The base station may repeat the operations without sending another request from the UE at block 706 or sending another A-TRS configuration to the UE at block 707. From the A-TRS, the UE may again be able to obtain alignment or synchronization of power and waveform frequency / timing in the SSB-free secondary cell 704, and thereafter the UE may again receive downlink data in the SSB-free secondary cell 704, as previously described (e.g., operations with respect to blocks 712, 714, and 716).

[0093] Fig. 9 An example 900 of a call flow between a UE 902 and a base station 904 communicating via a primary component carrier (PCC) 908 in an anchor cell 906 and via a secondary component carrier (SCC) 912 in a non-SSB secondary cell 910 is illustrated. The anchor cell 906 or PCC 908 may be on one frequency band 914, and the non-SSB secondary cell 910 or SCC 912 may be on another different frequency band 916.

[0094] Initially, UE 902 sends an A-TRS request 918 to base station 904 in anchor cell 906. A-TRS request 918 may correspond to UE Figure 7 In response to the A-TRS request 918, the base station 904 sends an A-TRS configuration 920 to the UE 902 in the anchor cell 906. The A-TRS configuration 920 may correspond to the base station sending the A-TRS request 918 to the UE 902 in the anchor cell 906. Figure 7The configuration sent at block 707 of Figure 8 The base station 904 may also send an A-TRS trigger 922 (e.g., DCI) to the UE 902 in the anchor cell 906. The A-TRS trigger 922 may correspond to the base station sending an A-TRS trigger 922 to the UE 902 in the anchor cell 906. Figure 7 The base station 904 may also set a timer 924 for A-TRS transmission in the SSB-free secondary cell 910 in response to the A-TRS trigger 922. The timer 924 may correspond to Figure 7 Timer 708 in.

[0095] When the timer 924 runs, the base station 904 may send an A-TRS 926 and a PDSCH 928 to the UE 902 in the SSB-free secondary cell 910. The transmission of the A-TRS 926 and the PDSCH 928 may correspond to Figure 7 If downlink data transmission is still ongoing, the base station 904 may send a subsequent A-TRS trigger 930 to the UE 902 in the non-SSB secondary cell 910 and reset the timer 924. The subsequent A-TRS trigger 930 may correspond to the base station sending the same signal at block 712 of FIG. Figure 7 The self-scheduling trigger sent at block 714 of . While the timer 924 keeps running, the base station 904 may send a subsequent A-TRS 932 and a subsequent PDSCH 934 to the UE 902 in the non-SSB secondary cell 910. The transmission of the subsequent A-TRS 932 and the subsequent PDSCH 934 may correspond to Figure 7 The sending of the same signal at box 716.

[0096] If no downlink data transmission is pending, the base station 904 may stop sending A-TRS to the UE 902, and the timer 924 may expire. After the expiration of the timer 924, if the base station 904 has new downlink data to send to the UE 902, the base station 904 may again send a subsequent A-TRS trigger 936 to the UE 902 in the anchor cell 906. The subsequent A-TRS trigger 936 may correspond to the base station sending the A-TRS to the UE 902 in the anchor cell 906. Figure 7 The base station 904 may also reset the timer 924 in response to a subsequent A-TRS trigger 936.

[0097] Fig.101000 is a flow chart of a wireless communication method. The method may be performed by a UE (e.g., UE 104, 350, 902; device 1202). Optional aspects are illustrated by dashed lines. The method allows the UE to request the base station in the anchor carrier to configure and send A-TRS transmission in the non-SSB secondary carrier for improved reception performance of downlink data transmission in the secondary carrier, thereby allowing network energy savings provided by the non-SSB secondary carrier to be obtained in inter-band CA.

[0098] At 1002, the UE may send a request for an A-TRS in a first cell. For example, 1002 may be performed by a request component 1240. For example, referring to the drawings, at block 706, the UE 902 may send an A-TRS request 918 for an A-TRS 504, 614 (e.g., an A-TRS burst 502) in an anchor cell 602, 702, 906.

[0099] At 1004, the UE may receive a configuration of the A-TRS in the first cell in response to the request. For example, 1004 may be performed by the configuration component 1242. For example, referring to the figure, at block 707, the UE 902 may receive an A-TRS configuration 920 in the anchor cell 602, 702, 906 in response to the A-TRS request 918.

[0100] In one example, the configuration may include at least one of: a resource set configuration for the A-TRS, or an A-CSI-RS triggering state for the A-TRS. In one example, the resource set configuration may include at least one of: an NZP-CSI-RS resource set for an A-TRS burst, the number of A-TRS bursts in the transmission opportunity of the A-TRS, or a time gap between each of the A-TRS bursts. For example, referring to the accompanying drawings, the A-TRS configuration 920 received by the UE 902 at box 707 may include, for example, a resource set configuration for the A-TRS 504, 614, such as an NZP-CSI-RS resource set configuration for a multi-burst A-TRS (e.g., the A-TRS burst 502), and an A-CSI-RS triggering state configuration for the A-TRS 504, 614. The NZP CSI-RS resource set configuration may include, for example, an NZP-CSI-RS resource set for an A-TRS burst (e.g., TRS burst 804), the number of A-TRS bursts in a transmission opportunity (e.g., transmission opportunity 805 at box 712, transmission opportunity 805 at box 716), and a time slot gap between A-TRS bursts (e.g., the time period included in the gap time slot 806).

[0101] At 1006, the UE may receive in the first cell a trigger for an A-TRS in a second cell that follows the configured lack of SSB transmission. For example, 1006 may be performed by a trigger component 1244. For example, referring to the drawings, at block 710, the UE 902 may receive an A-TRS trigger 922 in an anchor cell 602, 702, 906 that schedules or activates an A-TRS 504, 614 in a secondary cell 604, 704, 910 without SSB after the UE receives the A-TRS configuration 920.

[0102] In one example, the trigger is a DCI. In one example, the trigger includes a serving cell index for the second cell and a trigger state for the A-TRS. For example, referring to the accompanying drawings, the A-TRS trigger 922 may be a DCI (PDCCH) in the anchor cell 702 that schedules the A-TRS transmission in the SSB-free secondary cell 704. The trigger PDCCH may include parameters such as a secondary cell index for the SSB-free secondary cell 704 (the target SCell for cross-carrier scheduling) and an A-TRS trigger state.

[0103] In one example, the first cell may be an anchor cell served by a first component carrier in a first frequency band, and the second cell may be a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band. For example, referring to the drawings, the anchor cells 602, 702, 906 may be served by an anchor carrier 402 (e.g., PCC 908) in one frequency band 916 (e.g., 2 GHz band), and the SSB-free secondary cells 604, 704, 910 may be served by a SSB-free secondary carrier 406 (e.g., SCC 912) in a different frequency band 914 (e.g., 3 GHz band).

[0104] In one example, the request may include UE assistance information indicating at least one of the following: a second cell in which the A-TRS is to be received, a bandwidth associated with the A-TRS, a number of A-TRS bursts in a transmission opportunity including the A-TRS, a number of time slots for each of the A-TRS bursts, or a time gap between each of the A-TRS bursts. For example, referring to the accompanying drawings, the A-TRS request 918 sent by the UE 902 at block 706 may be signaled via a MAC-CE or RRC message (e.g., UE assistance information signaling) and include parameters or information that the base station 904 may use to configure the A-TRS 504, 614. For example, one parameter that the UE 902 may indicate in the A-TRS request 918 is a target secondary cell for A-TRS transmission (e.g., an index of a non-SSB secondary cell 604, 704, 910). Another parameter that the UE 902 may indicate in the A-TRS request 918 is a TRS bandwidth (the bandwidth of the A-TRS transmission). Other parameters that the UE 902 may indicate in the A-TRS request 918 may include the number of time slots used for TRS bursts (e.g., one or two time slots per A-TRS burst), the number of TRS bursts (e.g., two TRS bursts), and the time slot spacing between TRS bursts (e.g., two time slots between TRS bursts). Figure 8 As illustrated, the UE may request the number of TRS slots 802 for TRS bursts 804 , the number of TRS bursts 804 that the base station is to transmit in a given transmit opportunity 805 , and the number of gap slots 806 between TRS bursts 804 .

[0105] In one example, the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including an A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or a maximum time period between a last A-TRS burst and downlink data transmission in the second cell. For example, referring to the accompanying drawings, the A-TRS request 918 sent by the UE 902 at block 706 may include one or more parameters related to a timer 708, 924, which is associated with a duration for which the base station 904 may send an A-TRS 504, 614 in the non-SSB secondary cell 604, 704, 910. One parameter or timeline information may include a minimum time gap between A-TRS transmission opportunities (e.g., between transmission opportunities 805 at blocks 712 and 716, respectively). For example, if the minimum time gap indicated in the UE request is 100 ms, then at block 716, the base station may send the multi-burst A-TRS no earlier than 100 ms after sending the multi-burst A-TRS at block 712. Another parameter or timeline information may include a maximum time gap between the last burst of A-TRS transmission and subsequent PDCCH / PDSCH transmission in the SSB-free secondary cell 604, 704, 910 (e.g., between the last TRS burst 804 in the transmission opportunity 805 at block 712 and downlink data transmission in the SSB-free secondary cell). For example, if the maximum time gap indicated in the UE request is 200 ms, then at block 712 (or at block 716), the base station may send the PDSCH no later than 200 ms after the last A-TRS burst sent at block 712 (or at block 716, respectively).

[0106] In one example, the trigger that the UE may receive at 1006 may activate a timer based on the timeline information. For example, referring to the figure, based on the timeline information (e.g., the minimum time gap and / or the maximum time gap) provided by the UE in the A-TRS request 918, the base station 904 may determine the length of time (e.g., the value of the timer 708, 924) during which the base station may send the A-TRS 504, 614 in the SSB-free secondary cell 604, 704, 910. Using this determined length of time, the A-TRS trigger 922 sent by the base station 904 at block 710 may then set and activate the timer 708, 924 for A-TRS transmission in the SSB-free secondary cell 604, 704, 910.

[0107] At 1008, the UE may receive an A-TRS in a second cell lacking SSB transmission based on the request. For example, 1008 may be performed by the A-TRS component 1246. For example, referring to the figure, at block 712, the UE 902 may receive an A-TRS 926 in a secondary cell without SSB 604, 704, 910, and then receive a PDSCH 928. The A-TRS configuration 920 (e.g., such as Figure 8 800 ) receives an A-TRS 926 (eg, A-TRS 504 , 614 ) in one or more TRS bursts 804 , the configured parameters of which have been indicated by or derived from an A-TRS request 918 .

[0108] At 1010, after the timer is activated (e.g., by the trigger at 1006), the UE may receive in the second cell a subsequent trigger for a subsequent A-TRS in the second cell before expiration of the timer. The timer may be reset in response to the subsequent trigger. For example, 1010 may be performed by a subsequent trigger component 1248. For example, referring to the accompanying drawings, after the UE 902 receives the A-TRS trigger 922 in the anchor cell 602, 702, 906 at block 710, thereby activating the timer 708, 924, and while the timer 708, 924 is still running, there may still be pending (or additional) downlink data intended for the UE 902. Therefore, at block 714, the UE 902 may receive a subsequent A-TRS trigger 930 in the SSB-free secondary cell 604, 704, 910, which schedules or activates the A-TRS 504, 614 in the SSB-free secondary cell 604, 704, 910. For example, the base station 904 may send a DCI (PDCCH) in the non-SSB secondary cell 604, 704, 910 that schedules the transmission of the A-TRS 932 and the PDSCH 934 at block 716 in the same non-SSB secondary cell. The subsequent A-TRS trigger 930 sent by the base station 904 at block 714 may also reset the timer 708, 924 for the A-TRS transmission in the non-SSB secondary cell 604, 704, 910.

[0109] At 1012, after the timer is activated (e.g., by the trigger at 1006 or 1010), the UE may receive a subsequent trigger for a subsequent A-TRS in the second cell in the first cell after expiration of the timer. The timer may be reset in response to the subsequent trigger. For example, 1012 may be performed by a subsequent trigger component 1248. For example, referring to the drawings, after the UE 902 receives the A-TRS trigger 922 in the anchor cell 602, 702, 906 at block 710, thereby activating the timer 708, 924 (or after the UE 902 receives the subsequent A-TRS trigger 930 in the SSB-free secondary cell 604, 704, 910 at block 714, thereby reactivating the timer 708, 924), there may no longer be pending (or additional) downlink data intended for the UE 902, and therefore the timer 708, 924 may expire. Thus, the foregoing operations of cross-carrier A-TRS triggering at block 710 may be repeated, in which case the UE 902 may receive a subsequent A-TRS trigger 936 in the anchor cell 602, 702, 906 that schedules or activates the A-TRS 504, 614 in the non-SSB secondary cell 604, 704, 910. For example, the base station 904 may transmit a DCI (PDCCH) in the anchor cell 602, 702, 906 that schedules the transmission of the A-TRS and PDSCH in the non-SSB secondary cell 604, 704, 910. The subsequent A-TRS trigger 936 may also reset the timer 708, 924 for A-TRS transmission in the non-SSB secondary cell 604, 704, 910. Thus, after the timer is reset, the UE 902 may repeat the foregoing operations of A-TRS / PDSCH reception and the subsequent A-TRS triggering begins again at 1008.

[0110] Fig.11 1100 is a flow chart of a wireless communication method. The method may be performed by a base station (e.g., base station 102 / 180, 310, 904; device 1302). Optional aspects are illustrated by dashed lines. The method allows the base station to configure and send A-TRS transmissions in a non-SSB secondary carrier in response to a UE request in an anchor carrier for improved reception performance of downlink data transmissions in the secondary carrier, thereby allowing network energy savings provided by the non-SSB secondary carrier to be obtained in inter-band CA.

[0111] At 1102, the base station can receive a request for an A-TRS in a first cell. For example, 1102 can be performed by a request component 1340. For example, referring to the drawings, at block 706, the base station 904 can receive an A-TRS request 918 for an A-TRS 504, 614 (e.g., an A-TRS burst 502) in an anchor cell 602, 702, 906.

[0112] At 1104, the base station may send a configuration of the A-TRS in the first cell in response to the request. For example, 1104 may be performed by the configuration component 1342. For example, referring to the figure, at block 707, the base station 904 may send an A-TRS configuration 920 in the anchor cell 602, 702, 906 in response to the A-TRS request 918.

[0113] In one example, the configuration may include at least one of: a resource set configuration for the A-TRS, or an A-CSI-RS triggering state for the A-TRS. In one example, the resource set configuration may include at least one of: an NZP-CSI-RS resource set for an A-TRS burst, including the number of A-TRS bursts in the transmission opportunity of the A-TRS, or a time gap between each of the A-TRS bursts. For example, referring to the accompanying drawings, the A-TRS configuration 920 sent by the base station 904 at box 707 may include, for example, a resource set configuration for the A-TRS 504, 614, such as an NZP-CSI-RS resource set configuration for a multi-burst A-TRS (e.g., the A-TRS burst 502), and an A-CSI-RS triggering state configuration for the A-TRS 504, 614. The NZP CSI-RS resource set configuration may include, for example, an NZP-CSI-RS resource set for an A-TRS burst (e.g., TRS burst 804), the number of A-TRS bursts in a transmission opportunity (e.g., transmission opportunity 805 at box 712, transmission opportunity 805 at box 716), and a time slot gap between A-TRS bursts (e.g., the time period included in the gap time slot 806).

[0114] At 1106, the base station may send a trigger for A-TRS in the second cell following the configured lack of SSB transmission in the first cell. For example, 1106 may be performed by the trigger component 1344. For example, referring to the drawings, at block 710, the base station 904 may send an A-TRS trigger 922 in the anchor cell 602, 702, 906, which schedules or activates the A-TRS 504, 614 in the SSB-free secondary cell 604, 704, 910 after the base station sends the A-TRS configuration 920.

[0115] In one example, the trigger is a DCI. In one example, the trigger includes a serving cell index for the second cell and a trigger state for the A-TRS. For example, referring to the accompanying drawings, the A-TRS trigger 922 may be a DCI (PDCCH) in the anchor cell 702 that schedules the A-TRS transmission in the SSB-free secondary cell 704. The trigger PDCCH may include parameters such as a secondary cell index for the SSB-free secondary cell 704 (the target SCell for cross-carrier scheduling) and an A-TRS trigger state.

[0116] In one example, the first cell may be an anchor cell served by a first component carrier in a first frequency band, and the second cell may be a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band. For example, referring to the drawings, the anchor cells 602, 702, 906 may be served by an anchor carrier 402 (e.g., PCC 908) in one frequency band 916 (e.g., 2 GHz band), and the SSB-free secondary cells 604, 704, 910 may be served by a SSB-free secondary carrier 406 (e.g., SCC 912) in a different frequency band 914 (e.g., 3 GHz band).

[0117] In one example, the request may include UE assistance information indicating at least one of the following: a second cell in which the A-TRS is to be received, a bandwidth associated with the A-TRS, a number of A-TRS bursts in a transmission opportunity including the A-TRS, a number of time slots for each of the A-TRS bursts, or a time gap between each of the A-TRS bursts. For example, referring to the accompanying drawings, the A-TRS request 918 received by the base station 904 at block 706 may be signaled via a MAC-CE or RRC message (e.g., UE assistance information signaling) and include parameters or information that the base station 904 may use to configure the A-TRS 504, 614. For example, one parameter that the UE 902 may indicate in the A-TRS request 918 is a target secondary cell for A-TRS transmission (e.g., an index of a non-SSB secondary cell 604, 704, 910). Another parameter that the UE 902 may indicate in the A-TRS request 918 is a TRS bandwidth (the bandwidth of the A-TRS transmission). Other parameters that the UE 902 may indicate in the A-TRS request 918 may include the number of time slots used for TRS bursts (e.g., one or two time slots per A-TRS burst), the number of TRS bursts (e.g., two TRS bursts), and the time slot spacing between TRS bursts (e.g., two time slots between TRS bursts). Figure 8 As illustrated, the UE may request the number of TRS slots 802 for TRS bursts 804 , the number of TRS bursts 804 that the base station is to transmit in a given transmit opportunity 805 , and the number of gap slots 806 between TRS bursts 804 .

[0118] In one example, the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including an A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or a maximum time period between a last A-TRS burst and downlink data transmission in the second cell. For example, referring to the accompanying drawings, the A-TRS request 918 received by the base station 904 at block 706 may include one or more parameters related to timers 708, 924, which are associated with a duration for which the base station 904 may transmit A-TRS 504, 614 in the non-SSB secondary cell 604, 704, 910. One parameter or timeline information may include a minimum time gap between A-TRS transmission opportunities (e.g., between transmission opportunities 805 at blocks 712 and 716, respectively). For example, if the minimum time gap indicated in the UE request is 100 ms, then at block 716, the base station may transmit the multi-burst A-TRS no earlier than 100 ms after the multi-burst A-TRS is transmitted at block 712. Another parameter or timeline information may include a maximum time gap between the last burst of A-TRS transmission and subsequent PDCCH / PDSCH transmission in the SSB-free secondary cell 604, 704, 910 (e.g., between the last TRS burst 804 in the transmission opportunity 805 at block 712 and downlink data transmission in the SSB-free secondary cell). For example, if the maximum time gap indicated in the UE request is 200 ms, then at block 712 (or at block 716), the base station may send the PDSCH no later than 200 ms after the last A-TRS burst sent at block 712 (or at block 716, respectively).

[0119] In one example, the trigger that the base station can send at 1106 can activate a timer based on the timeline information. For example, referring to the figure, based on the timeline information (e.g., the minimum time gap and / or the maximum time gap) provided by the UE in the A-TRS request 918, the base station 904 can determine the length of time (e.g., the value of the timer 708, 924) during which the base station can send the A-TRS 504, 614 in the SSB-free secondary cell 604, 704, 910. Using this determined length of time, the A-TRS trigger 922 sent by the base station 904 at block 710 can then set and activate the timer 708, 924 for A-TRS transmission in the SSB-free secondary cell 604, 704, 910.

[0120] At 1108, the base station may transmit an A-TRS in the second cell lacking SSB transmission based on the request. For example, 1108 may be performed by the A-TRS component 1346. For example, referring to the figure, at block 712, the base station 904 may transmit an A-TRS 926 in the secondary cell 604, 704, 910 without SSB, followed by a PDSCH 928. The A-TRS configuration 920 (e.g., such as Figure 8 800 ) sends an A-TRS 926 (eg, A-TRS 504 , 614 ) in one or more TRS bursts 804 , the configured parameters of which have been indicated by or derived from an A-TRS request 918 .

[0121] At 1110, after the timer is activated (e.g., by the trigger at 1106), the base station may send a subsequent trigger for receiving a subsequent A-TRS in the second cell in the second cell before the expiration of the timer. The timer may be reset in response to the subsequent trigger. For example, 1110 may be performed by a subsequent trigger component 1348. For example, referring to the accompanying drawings, after the UE 902 receives the A-TRS trigger 922 in the anchor cell 602, 702, 906 at box 710, thereby activating the timer 708, 924, and while the timer 708, 924 is still running, there may still be pending (or additional) downlink data intended for the UE 902. Therefore, at box 714, the base station 904 may send a subsequent A-TRS trigger 930 in the SSB-free secondary cell 604, 704, 910, which schedules or activates the A-TRS 504, 614 in the SSB-free secondary cell 604, 704, 910. For example, the base station 904 may send a DCI (PDCCH) in the non-SSB secondary cell 604, 704, 910 that schedules the transmission of the A-TRS 932 and the PDSCH 934 at block 716 in the same non-SSB secondary cell. The subsequent A-TRS trigger 930 sent by the base station 904 at block 714 may also reset the timer 708, 924 for the A-TRS transmission in the non-SSB secondary cell 604, 704, 910.

[0122] At 1112, after the timer is activated (e.g., by the trigger at 1106 or 1110), the base station may send a subsequent trigger for a subsequent A-TRS in the second cell in the first cell after expiration of the timer. The timer may be reset in response to the subsequent trigger. For example, 1112 may be performed by a subsequent trigger component 1348. For example, referring to the drawings, after the UE 902 receives the A-TRS trigger 922 in the anchor cell 602, 702, 906 at block 710, thereby activating the timer 708, 924 (or after the UE 902 receives the subsequent A-TRS trigger 930 in the SSB-free secondary cell 604, 704, 910 at block 714, thereby reactivating the timer 708, 924), there may no longer be pending (or additional) downlink data intended for the UE 902, and therefore the timer 708, 924 may expire. Thus, the aforementioned operation of cross-carrier A-TRS triggering at block 710 may be repeated, in which case the base station 904 may send a subsequent A-TRS trigger 936 in the anchor cell 602, 702, 906 that schedules or activates the A-TRS 504, 614 in the SSB-free secondary cell 604, 704, 910. For example, the base station 904 may send a DCI (PDCCH) in the anchor cell 602, 702, 906 that schedules the transmission of the A-TRS and PDSCH in the SSB-free secondary cell 604, 704, 910. The subsequent A-TRS trigger 936 may also reset the timer 708, 924 for A-TRS transmission in the SSB-free secondary cell 604, 704, 910. Thus, after the timer is reset, the base station 904 may repeat the aforementioned operation of A-TRS / PDSCH transmission and the subsequent A-TRS triggering starts again at 1108.

[0123] Fig.121 is a diagram 1200 illustrating an example of a hardware implementation for an apparatus 1202. The apparatus 1202 is a UE and includes a cellular baseband processor 1204 (also referred to as a modem) coupled to a cellular RF transceiver 1222 and one or more subscriber identity modules (SIM) cards 1220, an application processor 1206 coupled to a secure digital (SD) card 1208 and a screen 1210, a Bluetooth module 1212, a wireless local area network (WLAN) module 1214, a global positioning system (GPS) module 1216, and a power supply 1218. The cellular baseband processor 1204 communicates with the UE 104 and / or the BS 102 / 180 via the cellular RF transceiver 1222. The cellular baseband processor 1204 may include a computer-readable medium / memory. The computer-readable medium / memory may be non-transitory. The cellular baseband processor 1204 is responsible for general processing, including executing software stored on the computer-readable medium / memory. The software, when executed by the cellular baseband processor 1204, causes the cellular baseband processor 1204 to perform the various functions described above. The computer-readable medium / memory may also be used to store data manipulated by the cellular baseband processor 1204 when executing the software. The cellular baseband processor 1204 also includes a receiving component 1230, a communication manager 1232, and a sending component 1234. The communication manager 1232 includes one or more of the illustrated components. The components within the communication manager 1232 may be stored in a computer-readable medium / memory and / or configured as hardware within the cellular baseband processor 1204. The cellular baseband processor 1204 may be a component of the UE 350 and may include a memory 360 and / or at least one of a TX processor 368, an RX processor 356, and a controller / processor 359. In one configuration, the device 1202 may be a modem chip and include only the baseband processor 1204, and in another configuration, the device 1202 may be the entire UE (e.g., see Figure 3 350), and includes the aforementioned additional modules of device 1202.

[0124] The communication manager 1232 includes a request component 1240 configured to send a request for an A-TRS in a first cell, e.g., as described in conjunction with 1002. The communication manager 1232 also includes a configuration component 1242 configured to receive a configuration of an A-TRS in the first cell in response to the request, e.g., as described in conjunction with 1004. The communication manager 1232 also includes a trigger component 1244 configured to receive a trigger of an A-TRS in the second cell in the first cell following the configured lack of SSB transmission, e.g., as described in conjunction with 1006. The communication manager 1232 also includes an A-TRS component 1246 configured to receive an A-TRS in the second cell in the lack of SSB transmission based on the request, e.g., as described in conjunction with 1008. The communication manager 1232 also includes a subsequent trigger component 1248 configured to receive, in the second cell before expiration of the timer, a subsequent trigger for a subsequent A-TRS in the second cell, wherein the timer is reset in response to the subsequent trigger, e.g., as described in conjunction with 1010. The subsequent trigger component 1248 is further configured to receive, in the first cell after expiration of the timer, a subsequent trigger for a subsequent A-TRS in the second cell, wherein the timer is reset in response to the subsequent trigger, e.g., as described in conjunction with 1012.

[0125] The apparatus may include executing Fig. 9 and Fig.10 Each of the boxes in the algorithm in the preceding flowchart is an additional component. Therefore, Fig. 9 and Fig.10 Each block in the aforementioned flow chart of can be performed by a component, and the apparatus may include one or more of these components. These components may be one or more hardware components, which are specifically configured to perform the process / algorithm, implemented by a processor configured to perform the process / algorithm, stored in a computer-readable medium so as to be implemented by a processor, or some combination thereof.

[0126] In one configuration, the device 1202 (and specifically the cellular baseband processor 1204) includes: a component for sending a request for an aperiodic tracking reference signal (A-TRS) in a first cell; and a component for receiving the A-TRS in a second cell in the absence of a synchronization signal block (SSB) transmission based on the request.

[0127] In one configuration, the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

[0128] In one configuration, the request includes UE assistance information indicating at least one of: the second cell in which the A-TRS will be received, the bandwidth associated with the A-TRS, the number of A-TRS bursts in which the A-TRS is transmitted, the number of time slots used for each of the A-TRS bursts, or the time gap between each of the A-TRS bursts.

[0129] In one configuration, the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including the A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or a maximum time period between a last A-TRS burst and downlink data transmission in the second cell. In one configuration, the means for receiving is further configured to receive, in response to the request, a trigger of the A-TRS in the second cell following an A-TRS configuration in the first cell, wherein the trigger activates a timer based on the timeline information.

[0130] In one configuration, the means for receiving is further configured to receive a configuration of the A-TRS in the first cell in response to the request; and receive in the first cell a trigger of the A-TRS in the second cell following the configuration.

[0131] In one configuration, the configuration includes at least one of: a resource set configuration for the A-TRS, or an aperiodic channel state information reference signal (A-CSI-RS) triggering state for the A-TRS. In one configuration, the resource set configuration includes at least one of: a non-zero power, channel state information reference signal (NZP-CSI-RS) resource set for an A-TRS burst, a number of A-TRS bursts in a transmission opportunity of the A-TRS, or a time gap between each of the A-TRS bursts.

[0132] In one configuration, the trigger activates a timer, and the means for receiving is further configured to receive in the second cell a subsequent trigger for a subsequent A-TRS in the second cell prior to expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0133] In one configuration, the trigger activates a timer, and the means for receiving is further configured to receive in the first cell a subsequent trigger for a subsequent A-TRS in the second cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0134] In one configuration, the trigger is downlink control information (DCI).

[0135] In one configuration, the trigger includes: a serving cell index for the second cell; and a trigger state for the A-TRS.

[0136] The aforementioned means may be one or more of the aforementioned components of the apparatus 1202 configured to perform the functions recited by the aforementioned means. As described above, the apparatus 1202 may include a TX processor 368, an RX processor 356, and a controller / processor 359. Therefore, in one configuration, the aforementioned means may be a TX processor 368, an RX processor 356, and a controller / processor 359 configured to perform the functions recited by the aforementioned means.

[0137] Fig.13 1300 is an example of a hardware implementation for an apparatus 1302. The apparatus 1302 is a BS and includes a baseband unit 1304. The baseband unit 1304 can communicate with the UE 104 via a cellular RF transceiver. The baseband unit 1304 may include a computer-readable medium / memory. The baseband unit 1304 is responsible for general processing, including executing software stored on the computer-readable medium / memory. The software, when executed by the baseband unit 1304, causes the baseband unit 1304 to perform the various functions described above. The computer-readable medium / memory can also be used to store data manipulated by the baseband unit 1304 when executing the software. The baseband unit 1304 also includes a receiving component 1330, a communication manager 1332, and a sending component 1334. The communication manager 1332 includes one or more of the illustrated components. The components within the communication manager 1332 may be stored in a computer-readable medium / memory and / or configured as hardware within the baseband unit 1304. The baseband unit 1304 may be a component of the BS 310 and may include a memory 376 and / or at least one of the TX processor 316 , the RX processor 370 , and the controller / processor 375 .

[0138] The communication manager 1332 includes a request component 1340 configured to receive a request for an A-TRS in a first cell, e.g., as described in conjunction with 1102. The communication manager 1332 also includes a configuration component 1342 configured to send a configuration of the A-TRS in the first cell in response to the request, e.g., as described in conjunction with 1104. The communication manager 1332 also includes a trigger component 1344 configured to send a trigger of the A-TRS in the first cell following the configured lack of SSB transmission in the second cell, e.g., as described in conjunction with 1106. The communication manager 1332 also includes an A-TRS component 1346 configured to send the A-TRS in the second cell lacking SSB transmission based on the request, e.g., as described in conjunction with 1108. The communication manager 1332 also includes a subsequent trigger component 1348 configured to send a subsequent trigger for a subsequent A-TRS in the second cell before expiration of the timer, wherein the timer is reset in response to the subsequent trigger, e.g., as described in conjunction with 1110. The subsequent trigger component 1348 is further configured to send a subsequent trigger for a subsequent A-TRS in the second cell in the first cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger, e.g., as described in conjunction with 1112.

[0139] The apparatus may include executing Fig. 9 and Fig.11 Each of the boxes in the algorithm in the preceding flowchart is an additional component. Therefore, Fig. 9 and Fig.11 Each block in the aforementioned flow chart of can be performed by a component, and the apparatus may include one or more of these components. These components may be one or more hardware components, which are specifically configured to perform the process / algorithm, implemented by a processor configured to perform the process / algorithm, stored in a computer-readable medium so as to be implemented by a processor, or some combination thereof.

[0140] In one configuration, the apparatus 1302 (and specifically the baseband unit 1304) includes: a component for receiving a request for an aperiodic tracking reference signal (A-TRS) in a first cell; and a component for sending the A-TRS in a second cell in the absence of synchronization signal block (SSB) transmission based on the request.

[0141] In one configuration, the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

[0142] In one configuration, the request includes UE assistance information indicating at least one of: the second cell in which the A-TRS will be received, the bandwidth associated with the A-TRS, the number of A-TRS bursts in which the A-TRS is transmitted, the number of time slots used for each of the A-TRS bursts, or the time gap between each of the A-TRS bursts.

[0143] In one configuration, the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including the A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or a maximum time period between a last A-TRS burst and downlink data transmission in the second cell. In one configuration, the means for transmitting is further configured to transmit, in response to the request, a trigger of the A-TRS in the second cell following an A-TRS configuration, wherein the trigger activates a timer based on the timeline information.

[0144] In one configuration, the means for transmitting is further configured to transmit a configuration of the A-TRS in the first cell in response to the request; and transmit a trigger of the A-TRS in the second cell in the first cell following the configuration.

[0145] In one configuration, the configuration includes at least one of: a resource set configuration for the A-TRS, or an aperiodic channel state information reference signal (A-CSI-RS) triggering state for the A-TRS. In one configuration, the resource set configuration includes at least one of: a non-zero power, channel state information reference signal (NZP-CSI-RS) resource set for an A-TRS burst, a number of A-TRS bursts in a transmission opportunity of the A-TRS, or a time gap between each of the A-TRS bursts.

[0146] In one configuration, the trigger activates a timer, and the means for transmitting is further configured to transmit in the second cell a subsequent trigger for a subsequent A-TRS in the second cell prior to expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0147] In one configuration, the trigger activates a timer, and the means for transmitting is further configured to transmit, in the first cell, a subsequent trigger for a subsequent A-TRS in the second cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0148] In one configuration, the trigger is downlink control information (DCI).

[0149] In one configuration, the trigger includes: a serving cell index for the second cell; and a trigger status for the A-TRS.

[0150] The aforementioned means may be one or more of the aforementioned components of the apparatus 1302 configured to perform the functions recited by the aforementioned means. As described above, the apparatus 1302 may include a TX processor 316, an RX processor 370, and a controller / processor 375. Therefore, in one configuration, the aforementioned means may be a TX processor 316, an RX processor 370, and a controller / processor 375 configured to perform the functions recited by the aforementioned means.

[0151] Therefore, various aspects of the present disclosure allow a UE to request (e.g., via UE assistance information) a base station to provide an A-TRS configuration indicating various parameters of an A-TRS that the base station will send in an SSB-free secondary cell, and allow the base station to control the transmission of the A-TRS in the SSB-free secondary cell based on a timer derived from the request. In addition, various aspects of the present disclosure allow the base station to trigger the transmission of the A-TRS in the SSB-free secondary cell via cross-carrier scheduling (e.g., using a DCI in an anchor cell that triggers the A-TRS in the SSB-free secondary cell) before the start of the timer or after the expiration of the timer derived from the request. In addition, various aspects of the present disclosure allow the base station to trigger the transmission of the A-TRS in the SSB-free secondary cell via self-scheduling (e.g., using a DCI in an SSB-free secondary cell that triggers the A-TRS and schedules the PDSCH in the SSB-free secondary cell) before the expiration of the timer derived from the request. Therefore, the network energy savings provided by the SSB-free secondary cell can be accommodated in inter-band CA.

[0152] It should be understood that the specific order or hierarchy of the blocks in the disclosed process / flowchart is merely an illustration of the exemplary method. It should be understood that the specific order or hierarchy of the blocks in the process / flowchart may be rearranged based on design preferences. Further, some blocks may be combined or omitted. The attached method claims provide the elements of each block in a sample order, but are not meant to be limited to the specific order or hierarchy provided.

[0153] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but to conform to the full scope consistent with the language claims, wherein unless otherwise specified, the elements mentioned in the singular are not intended to represent "one and only one", but "one or more". Terms such as "if", "when ..." and "while ..." should be interpreted as "under the conditions of ...", rather than meaning an instantaneous time relationship or reaction. That is, these phrases, such as "when ...", do not mean an instantaneous action in response to the occurrence of an action or during the occurrence of an action, but simply imply that if the conditions are met, the action will occur, but no specific or instantaneous time limit is required for the occurrence of the action. The word "exemplary" is used herein to mean "used as an example, instance, or illustration". Any aspect described as "exemplary" herein is not necessarily interpreted as being preferred or having an advantage over other aspects. Unless otherwise specified, the term "some" refers to one or more. Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, and / or C, which may include multiple A, multiple B, or multiple C. Specifically, combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” may be only A, only B, only C, A and B, A and C, B and C, or A and B and C, where any such combination may include one or more members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout the disclosure that are known or later become known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be dedicated to the public, regardless of whether such disclosure is explicitly recited in the claims. Words such as "module," "mechanism," "element," "device," etc. cannot replace the word "component." Therefore, no claim element will be construed as part-plus-function unless the element is explicitly recited using the phrase "component for..."

[0154] The following examples are merely illustrative and may be combined with aspects of other embodiments or teachings described herein, but are not limited thereto.

[0155] Clause 1. An apparatus for wireless communication, the apparatus comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and operable when executed by the processor to cause the apparatus to: send a request for a non-periodic tracking reference signal (A-TRS) in a first cell; and receive the A-TRS in a second cell in the absence of a synchronization signal block (SSB) transmission based on the request.

[0156] Clause 2. The apparatus of clause 1, wherein the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

[0157] Clause 3. An apparatus according to clause 1 or clause 2, wherein the request includes UE assistance information indicating at least one of: the second cell in which the A-TRS will be received, the bandwidth associated with the A-TRS, the number of A-TRS bursts in which the A-TRS is transmitted, the number of time slots used for each of the A-TRS bursts, or the time gap between each of the A-TRS bursts.

[0158] Clause 4. An apparatus according to any one of clauses 1 to 3, wherein the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including the A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or a maximum time period between a last A-TRS burst and downlink data transmission in the second cell.

[0159] Clause 5. An apparatus according to clause 4, wherein the instructions, when executed by the processor, further cause the apparatus to: receive in the first cell a trigger of the A-TRS in the second cell following the A-TRS configuration in response to the request, wherein the trigger activates a timer based on the timeline information.

[0160] Clause 6. An apparatus according to any one of clauses 1 to 5, wherein the instructions, when executed by the processor, further cause the apparatus to: receive a configuration of the A-TRS in the first cell in response to the request; and receive in the first cell a trigger of the A-TRS in the second cell following the configuration.

[0161] Clause 7. The apparatus of clause 6, wherein the configuration comprises at least one of: a resource set configuration for the A-TRS, or an aperiodic channel state information reference signal (A-CSI-RS) triggering state for the A-TRS.

[0162] Clause 8. An apparatus according to clause 7, wherein the resource set configuration includes at least one of the following: a non-zero power, channel state information reference signal (NZP-CSI-RS) resource set for A-TRS bursts, including the number of A-TRS bursts in the transmission opportunity of the A-TRS, or the time gap between each of the A-TRS bursts.

[0163] Clause 9. An apparatus according to any one of clauses 6 to 8, wherein the trigger activates a timer, and the instruction, when executed by the processor, further causes the apparatus to: receive in the second cell a subsequent trigger for a subsequent A-TRS in the second cell before expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0164] Clause 10. An apparatus according to any one of clauses 6 to 9, wherein the trigger activates a timer, and the instruction, when executed by the processor, further causes the apparatus to: receive in the first cell a subsequent trigger for a subsequent A-TRS in the second cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0165] Clause 11. An apparatus as described in any of clauses 6 to 10, wherein the trigger is downlink control information (DCI).

[0166] Clause 12. An apparatus as described in any of clauses 6 to 11, wherein the trigger comprises: a serving cell index for the second cell; and a trigger state for the A-TRS.

[0167] Clause 13. An apparatus for wireless communication, the apparatus comprising: a processor; a memory coupled to the processor; and instructions stored in the memory and operable when executed by the processor to cause the apparatus to: receive a request for a non-periodic tracking reference signal (A-TRS) in a first cell; and send the A-TRS in a second cell in the absence of a synchronization signal block (SSB) transmission based on the request.

[0168] Clause 14. The apparatus of clause 13, wherein the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

[0169] Clause 15. An apparatus according to clause 13 or clause 14, wherein the request includes UE assistance information indicating at least one of the following: the second cell in which the A-TRS is to be sent, the bandwidth associated with the A-TRS, the number of A-TRS bursts in which the A-TRS is to be sent, the number of time slots used for each of the A-TRS bursts, or the time gap between each of the A-TRS bursts.

[0170] Clause 16. An apparatus according to any one of clauses 13 to 15, wherein the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including the A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or a maximum time period between a last A-TRS burst and downlink data transmission in the second cell.

[0171] Clause 17. An apparatus according to clause 16, wherein the instructions, when executed by the processor, further cause the apparatus to: send a trigger of the A-TRS in the second cell following the A-TRS configuration in response to the request in the first cell, wherein the trigger activates a timer based on the timeline information.

[0172] Clause 18. An apparatus according to any one of clauses 13 to 17, wherein the instructions, when executed by the processor, further cause the apparatus to: send a configuration of the A-TRS in the first cell in response to the request; and send a trigger of the A-TRS in the second cell in accordance with the configuration in the first cell.

[0173] Clause 19. The apparatus of clause 18, wherein the configuration comprises at least one of: a resource set configuration for the A-TRS, or an aperiodic channel state information reference signal (A-CSI-RS) triggering state for the A-TRS.

[0174] Clause 20. An apparatus according to clause 19, wherein the resource set configuration includes at least one of the following: a non-zero power, channel state information reference signal (NZP-CSI-RS) resource set for A-TRS bursts, including the number of A-TRS bursts in the transmission opportunity of the A-TRS, or the time gap between each of the A-TRS bursts.

[0175] Clause 21. An apparatus according to any one of clauses 18 to 20, wherein the trigger activates a timer, and the instruction, when executed by the processor, further causes the apparatus to: send a subsequent trigger for a subsequent A-TRS in the second cell in the second cell before expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0176] Clause 22. An apparatus according to any one of clauses 18 to 21, wherein the trigger activates a timer, and the instruction, when executed by the processor, further causes the apparatus to: send in the first cell a subsequent trigger for a subsequent A-TRS in the second cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0177] Clause 23. An apparatus as described in any of clauses 18 to 22, wherein the trigger is downlink control information (DCI).

[0178] Clause 24. An apparatus as described in any of clauses 18 to 23, wherein the trigger comprises: a serving cell index for the second cell; and a trigger state for the A-TRS.

[0179] Clause 25. A method of wireless communication at a user equipment (UE), the method comprising: sending a request for an aperiodic tracking reference signal (A-TRS) in a first cell; and receiving the A-TRS in a second cell in the absence of a synchronization signal block (SSB) transmission based on the request.

[0180] Clause 26. The method of clause 25, wherein the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

[0181] Clause 27. The method according to clause 25 or clause 26, the method further comprising: receiving a configuration of the A-TRS in the first cell in response to the request; and receiving a trigger of the A-TRS in the second cell in the first cell following the configuration.

[0182] Clause 28. A method according to clause 27, wherein the trigger activates a timer, and the method further comprises: receiving in the second cell a subsequent trigger for a subsequent A-TRS in the second cell before expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0183] Clause 29. A method according to clause 27 or clause 28, wherein the trigger activates a timer, and the method further comprises: receiving in the first cell a subsequent trigger for a subsequent A-TRS in the second cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

[0184] Clause 30. A method of wireless communication at a network entity, the method comprising: receiving a request for an aperiodic tracking reference signal (A-TRS) in a first cell; and sending the A-TRS in a second cell in the absence of synchronization signal block (SSB) transmission based on the request.

Claims

1. A device for wireless communication, the device comprising: processor; a memory coupled to the processor; and instructions stored in the memory and operable when executed by the processor to cause the apparatus to: sending a request for an aperiodic tracking reference signal (A-TRS) in the first cell; and The A-TRS is received in a second cell lacking synchronization signal block (SSB) transmission based on the request.

2. The apparatus of claim 1, wherein the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

3. The apparatus of claim 1 , wherein the request comprises UE assistance information indicating at least one of: wherein the second cell will receive the A-TRS, the bandwidth associated with the A-TRS, the number of A-TRS bursts in the transmission opportunities of the A-TRS, the number of time slots used for each of the A-TRS bursts, or A time gap between each of the A-TRS bursts.

4. The apparatus of claim 1 , wherein the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including the A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or The maximum time period between the last A-TRS burst and downlink data transmission in the second cell.

5. The apparatus of claim 4, wherein the instructions, when executed by the processor, further cause the apparatus to: A trigger of the A-TRS in the second cell following an A-TRS configuration is received in the first cell in response to the request, wherein the trigger activates a timer based on the timeline information.

6. The apparatus of claim 1, wherein the instructions, when executed by the processor, further cause the apparatus to: receiving configuration of the A-TRS in the first cell in response to the request; and A trigger of the A-TRS in the second cell following the configuration is received in the first cell.

7. The apparatus of claim 6, wherein the configuration comprises at least one of: a resource set configuration for the A-TRS, or An aperiodic channel state information reference signal (A-CSI-RS) triggering status for the A-TRS.

8. The apparatus of claim 7, wherein the resource set configuration comprises at least one of the following: The set of non-zero power, channel state information reference signal (NZP-CSI-RS) resources for A-TRS bursts, the number of A-TRS bursts including the A-TRS transmission opportunities, or A time gap between each of the A-TRS bursts.

9. The apparatus of claim 6, wherein the trigger activates a timer, and the instructions, when executed by the processor, further cause the apparatus to: A subsequent trigger for a subsequent A-TRS in the second cell is received in the second cell prior to expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

10. The apparatus of claim 6, wherein the trigger activates a timer, and the instructions, when executed by the processor, further cause the apparatus to: A subsequent trigger is received in the first cell for a subsequent A-TRS in the second cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

11. The apparatus of claim 6, wherein the trigger is downlink control information (DCI).

12. The apparatus of claim 6, wherein the trigger comprises: a serving cell index for the second cell; and The trigger status for the A-TRS.

13. An apparatus for wireless communication, the apparatus comprising: processor; a memory coupled to the processor; and instructions stored in the memory and operable when executed by the processor to cause the apparatus to: receiving a request for an aperiodic tracking reference signal (A-TRS) in a first cell; and The A-TRS is transmitted in a second cell lacking synchronization signal block (SSB) transmission based on the request.

14. The apparatus of claim 13, wherein the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

15. The apparatus of claim 13, wherein the request comprises UE assistance information indicating at least one of: the second cell in which the A-TRS is to be sent, the bandwidth associated with the A-TRS, the number of A-TRS bursts in the transmission opportunities of the A-TRS, the number of time slots used for each of the A-TRS bursts, or A time gap between each of the A-TRS bursts.

16. The apparatus of claim 13, wherein the request includes timeline information indicating at least one of: a minimum time period between a first transmission opportunity including the A-TRS and a second transmission opportunity including a subsequent A-TRS in the second cell, or The maximum time period between the last A-TRS burst and downlink data transmission in the second cell.

17. The apparatus of claim 16, wherein the instructions, when executed by the processor, further cause the apparatus to: A trigger for the A-TRS in the second cell following an A-TRS configuration is sent in the first cell in response to the request, wherein the trigger activates a timer based on the timeline information.

18. The apparatus of claim 13, wherein the instructions, when executed by the processor, further cause the apparatus to: sending the configuration of the A-TRS in the first cell in response to the request; and A trigger of the A-TRS in the second cell following the configuration is sent in the first cell.

19. The apparatus of claim 18, wherein the configuration comprises at least one of: a resource set configuration for the A-TRS, or An aperiodic channel state information reference signal (A-CSI-RS) triggering status for the A-TRS.

20. The apparatus of claim 19, wherein the resource set configuration comprises at least one of: The set of non-zero power, channel state information reference signal (NZP-CSI-RS) resources for A-TRS bursts, the number of A-TRS bursts including the A-TRS transmission opportunities, or A time gap between each of the A-TRS bursts.

21. The apparatus of claim 18, wherein the trigger activates a timer, and the instructions, when executed by the processor, further cause the apparatus to: A subsequent trigger for a subsequent A-TRS in the second cell is sent in the second cell before expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

22. The apparatus of claim 18, wherein the trigger activates a timer, and the instructions, when executed by the processor, further cause the apparatus to: A subsequent trigger for a subsequent A-TRS in the second cell is sent in the first cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

23. The apparatus of claim 18, wherein the trigger is downlink control information (DCI).

24. The apparatus of claim 18, wherein the trigger comprises: a serving cell index for the second cell; and The trigger status for the A-TRS.

25. A method of wireless communication at a user equipment (UE), the method comprising: sending a request for an aperiodic tracking reference signal (A-TRS) in a first cell; as well as The A-TRS is received in a second cell lacking synchronization signal block (SSB) transmission based on the request.

26. The method of claim 25, wherein the first cell is an anchor cell served by a first component carrier in a first frequency band, and the second cell is a secondary cell served by a second component carrier in a second frequency band, the second frequency band being different from the first frequency band.

27. The method according to claim 25, further comprising: receiving, in response to the request, configuration of the A-TRS in the first cell; as well as A trigger of the A-TRS in the second cell following the configuration is received in the first cell.

28. The method of claim 27, wherein the trigger activates a timer, and the method further comprises: A subsequent trigger for a subsequent A-TRS in the second cell is received in the second cell prior to expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

29. The method of claim 27, wherein the trigger activates a timer, and the method further comprises: A subsequent trigger is received in the first cell for a subsequent A-TRS in the second cell after expiration of the timer, wherein the timer is reset in response to the subsequent trigger.

30. A method for wireless communication at a network entity, the method comprising: receiving, in a first cell, a request for an aperiodic tracking reference signal (A-TRS); as well as The A-TRS is transmitted in a second cell lacking synchronization signal block (SSB) transmission based on the request.

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